Most conventional magnetic recording media are of the coating type of magnetic recording media, and they are usually obtained by coating on a non-magnetic support a magnetic powder made up of a magnetic oxide, a magnetic alloy or the like together with a binder such as a vinyl chloride-vinyl acetate copolymer, a styrene-butadiene copolymer, an epoxy resin, a polyurethane resin or so on, and then drying the resulting coat.
In recent years, the demand for high density recording has been increased and therewith, the so-called non-binder type of magnetic recording media, which have on non-magnetic supports thin films made up of ferromagnetic metals alone without containing any binders as described above which are formed using a vacuum evaporation technique, a sputtering technique, an ion plating technique, a metal plating technique or the like, having attracted the attention in this art (U.S. Pat. Nos. 2,671,034, 3,329,601, 3,342,633, 3,156,860 and 3,615,911).
However, a magnetic metal thin layer can be readily corroded, because the thin layer consists of clusters of magnetic metal particles having a column structure and therefore, voids are formed among column-shaped particles, and along these voids the corrosion tends to occur. Although the above-described defect is a serius problem to be solved since it lowered the reliability as a recording medium, solutions to this problem have not yet been found.